Radiotelegraphy



Nov. 18, 1924. 1,515, 70

L. F. FULLER RADIOTELEGRAPHY Filed Sept. 25, 1919 2 Sheets-Sheet 2 t\ jf 4 3 x g g T 4 T A? WITNESS INVENTOR 1,. F5 FULLER H/fi A TTORNE YSPatented Nov. l 1924.

UNHTD STATES I retain rarer @IFFH.

LEONARD IE FULLER, OF BARBERTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS,TO FEDERAL TELEGRAPH COMPANY, OF SAN FRANCISCO, CALIFORNIA, A CORIORATION OF CALIFORNIA.

RADIOTELEGRAPHY.

Application filed September 25, 1919. Serial No. 326,3 44.

To all whom it may concern Be it known that I, LEONARD F. FULLER, acitizen of the United States, and a resident of Barberton, county ofSummit, and State 5 of Ohio, have invented certain new and usefulImprovements in Radiotelegraphy, of

ground systems of these stations has presented a very serious problem,since as the antenna currents used in practice has been constantlyincreased, the PR losses have become too large. Furthermore, the ratioof the energy radiated, i. e., 1 7' (rzradiation resistance) to PR(Rzohmic resistance of station ground system) has been so low, that theoverall efficiency of the stations has been below that value which couldbe considered reasonably satisfactory.

It is an object of my invention, therefore, to reduce the ohmicresistance of the ground system, and raise the overall efliciency of thestation.

Another object of my invention is to provide a radiating system whichwill transmit in a chosen direction instead of throughout 360, as is nowusually the case.

A further object of the invention is to provide an antenna whichrequires-a lesser number of towers for its support than do the highpowered antennae now employed.

The invention possesses otheradvantageous features, some of which, withthe foregoing,

will be set forth at length in the following description, where I shalloutline in full, thatiform of the invention which I have selected forillustration in the drawings accompanying and forming part of thepresent 5 specification. In said drawings I have shown one form of thesystem of my invention, but it is to be understood that I do not limitmyself to such form, since the invention, as expressed in the claims,may be embodied in a pluralityof forms.

Referring to said drawings:

Figure 1 is a diagram illustrating the principle of .my invention.

FlQ'UIP; 2 is a diagrammatic representation of a modified form oftransmission system of my invention.

Figure 3 is a diagrammatic representation of a further modified form oftransmission system of my invention.

Figure 4 is a diagrammatic representation in perspective of a system fortransmis sion in different directions, the loop circuits in one planebeing shown heavy and the loop circuits in the other plane being shownin light lines, to distinguish them.

The present invention involves the use of loop antenna. Theoreticalconsideration of the method by which energy is radiated from a loopantenna shows that among other things, the watts radiated from the loopare proportional to the square of the length of the loop and the squareof the number of turns. The radiated energy is also proportional to thesquare of the radio frequency current in the loop. Other conditionsremaining constant, it is evident that the watts radiated from the loopwill be quadrupled if the number of turns in the loop are doubled. Thisincrease in the number of turns, however, quadruples the reactivevoltage drop across the loop when the current is maintained constant.This increase in voltage is objectionable, since the maximum voltage inthe loop is rather definitely fixed by the allowable voltage on thecondenser in theloop circuit.

Theenergy radiated, however, may be increased without increasing thevoltage on the condenser by using two or more separate loops withcurrents in phase with each other arranged in the same vertical plane.

In Fig. 1 I have shown this diagrammatically. The radiating systemconsists of three vertical loops 2, 3 and 4, arranged in the samevertical plane, pointing in the same direction. A radio frequencycurrent is circulated in each loop by a source of radio frequency E. M.F. 5, and it is assumed that by some means the currents are kept inphase. The currents in the adjacent conductors of the successive loopsare in phase opposition,

and the direction of current flow is the same in all of the loops. Themagnetic fields set up by each loop acting as a solenoid are in the samedirection, so that there is no flux linking more than one'loop, andtherefore the inductance of each loop is not increased by the presenceof the adjacent loops. Hence the voltage on each loop is not increasedby the presence of adjacent loops. The inductive reactance of each loopis neutralized by a proper capacitance, 6, inserted in each loop, thecapacitance acting to tune the circuit.

The plurality of loopsmay be considered as one loop N times the lengthof a single loop, or as one loop having N turns. Since radiated Wattsare proportional to the square of the length of the loop or to thesquare of the number of turns of the loop, it follows that in eithercase the watts radiated are proportional to N It is also possible toarrange the loops in a various parallel planes with snflicient distancebetween them to reduce the mutual inductance to a very low value.

In Fig. 1 the sources of radio frequency E. M. F., 5, may be radiofreqency alternators connected mechanically, or otherwise, so that thecurrents in the three loops are in phase. It is not essential that therebe a source of radio freqency E. M. F. for each loop, and in Fig. 2 Ihave shown one source for three loops, this source consisting of aPoulsen are 15 fed by the D. C. generator 16, through a circuitcontaining a choke coil 17. In this arrangement, each loo is preferablyprovided with a variable inductor 8, by which each loop circuit istuned. The adjustments of each loop are made by varying the inductancein each loop circuit until the radio frequency ammeter 9 reads a maximumin accordance with the well-known method.

The loops are connected to the two buses, 12 and 13. Connected acrossthe buses, alternately with respect to the loops are the condensers 14and the inductors are so adjusted for each capacitance that there is aninductance of proper value to form a resonant circuit for the radiofrequency currents.

There are further methods of supplying energy to the loop radiatingsystem, which may be employed. The Poulsen are converter 15 may beinductively connected to the inductor 8 in the loop 2, in whicharrangement the inductance of each loop must be adjusted so that theperiod of oscillation of its respective loop is the same as the fre--.quency set up in the closed oscillatory circuit, containing the are 15,the condenser 18, and the inductor 19. This arrangement is shown in Fig.3.

Energy from the system of loops is radiated with maximum intensity inthe plane of the system, and with minimum'intensity normal to saidplane, the intensity at any angle with the plane being approximatelyproportional to the .cosine of the angle.

In Fig. 4 I show two loop systems at'right angles. If they are excitedby different sources of radio frequency E. M. F., two messages may besent at the same time on the same Wave length ;-one in the direction ofthe plane of one loop system and one in the plane of the other system."[In this figure I show the two loo-p systems connected to one source ofradio frequency thus permitting transmission of one message through-.v

condenser of extremely low resistance andv yet capable of withstandinghigh voltages.

Since the capacities used in this antenna system are near the earth, itis necessary that high towers, or masts, be provided only for thesupport of the loops, so that only one row of towels are required for astation which is constructed to send in. one direction.

It has been customary heretofore to put the capacitance as high in theair as possible, thereby throwing the electro-static field a longdistance: which in turn caused larger earth losses.

Signaling may well-known or desirable manner, and I do not desire tolimit myself in any manner to any particular method or apparatus forsignaling, In the drawings I have shown the signaling system disclosedin my United States Letters Patent No. 1,330,254, since this is one formof signaling system which may be employed with this antenna system,

although others may be used with equal or greater eflicacy.

I claim:

1. In a radio frequency transmission system, an ungrounded radiatingcircuit comprising a plurality of vertical loops in substantially thesame plane, the vertical sides of adjacent loops being near each other,

be accomplished in any means for supplying current to each loop,

of such phase that the currents in these adjacent vertical sides areopposed and substantially nullify. each other, whereby the resistancelosses in the entire structure may be maintained at a desired low value,and means for individually tuning the loops.

9. A radio telcgraphy transmission system comprising apluralityofycrtical loops arranged with their planes pointing in the samedirection, a pair of conductors to which the opposite end of said loopsare connected, a condenser connected across said conductors at eachloop, and a source of radio frequency eleetromotive force connectedacross said conductors.

3. An antenna comprising two sets of vertical loops arranged at an angleto each other, the loops in each set arranged with their planes pointingin the same direction and so that the mutual inductance between theloops of a set is practically zero.

4. A radio telegraphy transmission system In testimony whereof, I havehereunto set comprising two sets of vertical loops ar- In hand atBarberton, Ohio, this 13th day ranged at an angle to each other, theloops of September, 1919. 1 in each set arranged with their planespoint- LEONARD F. FULLER.

5 ing in the same direction and means for im- In presence of pressing aradio frequency electro-motive Gno. L. H. Ron, force on said. loops. LURETIA STRONG FULLER.

